Metal‐Free Synthesis of Pyrazoles and Chromenopyrazoles from Hydrazones and Acetylenic Esters

Abstract

An efficient, metal‐free synthesis of pyrazoles and chromenopyrazoles from aldehyde hydrazones and acetylenic esters has been developed. A library of molecules with diverse functional groups has been synthesized using substituted hydrazones and alkynes, both symmetrical and unsymmetrical ones. The derivatives were isolated in moderate to good yields.

Metal‐free Synthesis of Trisubstituted Pyrazoles by the Reaction Between Hydrazones and Activated Olefins

“…Recently, we reported the synthesis of pyrazoles and chromenopyrazoles from aldehyde hydrazones and acetylenic esters. The synthesis of pyrazole was successful with both mono‐ and di‐substituted acetylenes at room temperature [11] . Subsequently, incorporation of salicylaldehyde hydrazone in the reaction afforded the hybrid polycycle, chromenopyrazole in one pot at an elevated temperature of 70 °C.…”

Direct Access for the Regio- and Stereoselective Synthesis of N-Alkenylpyrazoles and Chromenopyrazoles

“…Pyrazole heterocyclic compounds are an attractive class of compounds and are key components of several drug molecules (Celebrex, Viagra, Zometapine, Cyenopyrafen, Fenpyroximate, Tebufenpyrad, Apixaban) and insecticide (Fipronil) . Pyrazole compounds possess a broad spectrum of biological properties, − serve as ligands in coordination chemistry, and act as optical brighteners. , Therefore, synthesis of pyrazoles has become an important area of study.…”

An elegant and efficient synthesis of heterocycles integrated with bis‐N‐acyl pyrazoline and bis‐1, 2, 3‐triazole via a green synthetic methodology

“…There are several reports which provide diverse synthetic protocols to synthesize N-substituted pyrazolines and/or triazole derivatives, which suffer from several short comings such as prolonged reaction time, multistep protocols, use of hazardous solvents, and expensive catalysts [31][32][33][34][35][36]. In view of this, we herein report our investigation toward the development of multicomponent reaction by mechanochemical solvent-free approach which overcome most of the demerits of conventional methodology.…”